The goal of this proposal is to understand the mechanisms of cell transformation by the human T cell leukemia viruses types I and II (HIV-I and II). The focus of research over the past two years has been in the p42 transactivator protein encoded by the pX region. The focus of attention in the coming years will be in the newly described pp27 and pp21 pX region encoded proteins. The structure and function of these proteins will be investigated. The combined effects of expression of all three proteins, p42, pp27, and pp21 on viral gene expression, on the expression of cellular genes, and on T cell transformation will also be investigated. The objectives of the proposal are: 1. To determine the structure and coding sequences of the pX encoded pp27 and pp21 protein. Specific aims include: a) development of specific antisera to the separate coding regions of pp27 and pp21; b) protein sequence analysis of the pp27 and pp21 proteins; c) characterization of the pp27 and pp21 messenger RNA species; d) large scale production and purification of the p42, pp27 and pp21 proteins. 2. To determine the role of the p42, pp27, and pp21 proteins in the regulation of viral gene expression. Specific aims include: a) construction of vectors that express the pp27 and pp21 proteins in transient transfection assays; b) construction of cell lines that express stably combinations of the p42, pp27, and pp21 proteins; c) analysis of the effects of these proteins on HIV-I and HIV-II LTR directed gene expression; d) fine mapping of the cis-acting regions within the LTR and viral genes responsive to the action of these proteins. 3. To determine the role of the p42, pp27, and pp21 proteins in regulation of cellular genes. Specific aims include: a) analysis of the altered gene expression in T and B cell lines that constitutively produce the pX encoded proteins singly or in combination. 4. To determine if primary lymphocytes can be transformed by pX region products. Specific aims include construction of new vectors suitable for primary cell transformation. It is expected that this work outlined in this proposal will take five years to complete.